The characteristics of spent nuclear fuel and high-level waste are described, and options for permanent disposal that have been considered are described. These include:
•disposal in a mined geological formation,
•disposal in a multinational repository, perhaps on an unoccupied island,
•by in situ melting, perhaps in underground nuclear test cavities,
•sub-seabed disposal,
•disposal in deep boreholes,
•disposal by melting through ice sheets or permafrost,
•disposal by sending the wastes into space, and

The purpose of this activity is to develop a representative “limiting” axial burnup profile for pressurized water reactors (PWRs), which would encompass the isotopic axial variations caused by different assembly irradiation histories, and produce conservative isotopics with respect to criticality. The effect that the low burnup regions near the ends of spent fuel have on system reactivity is termed the “end-effect”. This calculation will quantify the end-effects associated with Pressurized Water Reactor (PWR) fuel assemblies emplaced in a hypothetical 21 PWR waste package.

The purpose of this calculation is to develop axial profiles for estimating the axial variation in burnup of a boiling water reactor (BWR) assembly spent nuclear fuel (SNF) given the average burnup of an assembly. A discharged fuel assembly typically exhibits higher burnup in the center and lower burnup at the ends of the assembly. Criticality safety analyses taking credit for SNF burnup must account for axially varying burnup relative to calculations based on uniformly distributed assembly average burnup due to the under-burned tips.

The purpose of this activity is to develop a representative “limiting” axial burnup profile for pressurized water reactors (PWRs), which would encompass the isotopic axial variations caused by different assembly irradiation histories, and produce conservative isotopics with respect to

This technical report provides an updated summary of the waste package (WP) external criticalityrelated
risk of the plutonium disposition ceramic waste form, which is being developed and
evaluated by the Office of Fissile Materials Disposition of the U.S. Department of Energy (DOE).
The ceramic waste form consists of Pu immobilized in ceramic disks, which would be embedded
in High-Level Waste (HLW) glass in the HLW glass disposal canisters, known as the "can-incanister"

The objective of this analysis is to characterize the criticality safety aspects of a degraded Department of Energy spent nuclear fuel (DOE-SNF) canister containing Massachusetts Institute of Technology (MIT) or Oak Ridge Research (ORR) fuel in the Five-Pack Defense High-Level Waste (DHLW) waste package to demonstrate concept viability related to use in the Mined Geologic Disposal System (MGDS) environment for the postclosure time frame.

This calculation compares results from criticality evaluations for a 21-assembly pressurized water reactor (PWR) waste package based on 12 axial burnup profile representations for commercial spent nuclear fuel (SNF) assemblies. The burnup profiles encompass the axial variations caused by different fuel assembly irradiation histories in a commercial PWR, including end effects, and the concomitant effect on reactivity in the waste package. The bounding axial burnup profiles in Table T of reference 6.3 are used for this analysis.

In 1999, the United States Nuclear Regulatory Commission (U.S. NRC) initiated a research program
to support the development of technical bases and guidance that would facilitate the implementation of burnup
credit into licensing activities for transport and dry cask storage. This paper reviews the following major areas of
investigation: (1) specification of axial burnup profiles, (2) assumption on cooling time, (3) allowance for
assemblies with fixed and removable neutron absorbers, (4) the need for a burnup margin for fuel with initial